On Tue, 16 Dec 2014, Jakub Jelinek wrote:
> Hi!
>
> If for RSHIFT_EXPR vr0 is not VR_RANGE or is symbolic, currently we make
> the result VARYING, even when we can do much better just by trying to
> shift the min and max values down.
> Divisions/modulo already handles it similarly, and +/-/& also handle it.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Ok.
Thanks,
Richard.
> 2014-12-16 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/64322
> * tree-vrp.c (extract_range_from_binary_expr_1): Attempt to derive
> range for RSHIFT_EXPR even if vr0 range is not VR_RANGE or is symbolic.
>
> * gcc.dg/tree-ssa/vrp95.c: New test.
>
> --- gcc/tree-vrp.c.jj 2014-12-01 14:57:30.000000000 +0100
> +++ gcc/tree-vrp.c 2014-12-16 10:17:27.543111649 +0100
> @@ -2434,6 +2434,7 @@ extract_range_from_binary_expr_1 (value_
> && code != MAX_EXPR
> && code != PLUS_EXPR
> && code != MINUS_EXPR
> + && code != RSHIFT_EXPR
> && (vr0.type == VR_VARYING
> || vr1.type == VR_VARYING
> || vr0.type != vr1.type
> @@ -2948,6 +2949,15 @@ extract_range_from_binary_expr_1 (value_
> {
> if (code == RSHIFT_EXPR)
> {
> + /* Even if vr0 is VARYING or otherwise not usable, we can derive
> + useful ranges just from the shift count. E.g.
> + x >> 63 for signed 64-bit x is always [-1, 0]. */
> + if (vr0.type != VR_RANGE || symbolic_range_p (&vr0))
> + {
> + vr0.type = type = VR_RANGE;
> + vr0.min = vrp_val_min (expr_type);
> + vr0.max = vrp_val_max (expr_type);
> + }
> extract_range_from_multiplicative_op_1 (vr, code, &vr0, &vr1);
> return;
> }
> --- gcc/testsuite/gcc.dg/tree-ssa/vrp95.c.jj 2014-12-16 12:11:19.048361844
> +0100
> +++ gcc/testsuite/gcc.dg/tree-ssa/vrp95.c 2014-12-16 12:24:47.080308362
> +0100
> @@ -0,0 +1,50 @@
> +/* PR tree-optimization/64322 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-vrp1" } */
> +
> +extern void link_error ();
> +extern void required_check ();
> +
> +long long int
> +foo (long long int x)
> +{
> + x >>= sizeof (long long int) * __CHAR_BIT__ - 1;
> + if (x != 0 && x != -1)
> + link_error ();
> + return x;
> +}
> +
> +unsigned long long int
> +bar (unsigned long long int x)
> +{
> + x >>= sizeof (long long int) * __CHAR_BIT__ - 1;
> + if (x != 0 && x != 1)
> + link_error ();
> + return x;
> +}
> +
> +long long int
> +baz (long long int x)
> +{
> + x = (x >> sizeof (long long int) * __CHAR_BIT__ - 1) << 1;
> + x = x / 0x100000000LL;
> + if (x != 0)
> + link_error ();
> + return x;
> +}
> +
> +unsigned long long int
> +range (unsigned long long int x, int y)
> +{
> + y &= 3;
> + x >>= sizeof (long long int) * __CHAR_BIT__ - 1 - y;
> + if (x > 15)
> + link_error ();
> + if (x == 15)
> + required_check ();
> + return x;
> +}
> +
> +/* { dg-final { scan-tree-dump-not "link_error" "vrp1" } } */
> +/* { dg-final { scan-tree-dump "required_check" "vrp1" } } */
> +/* { dg-final { cleanup-tree-dump "vrp1" } } */
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Jennifer Guild,
Dilip Upmanyu, Graham Norton HRB 21284 (AG Nuernberg)
